Figure A.  In this case it was recognized that the person had three different reactions: a central induration, a somewhat larger edema and a large erythema.  Two errors are being made in reading.  First, the induration should be read transversely to the long axis of the arm (not along the axis as here).  Second, apparently the edema, not the induration is being measured.

Figure B.  This is the correct technique with a ruler.

Figure C.  Digit preference is a normal behavior:  People may unconsciously prefer even numbers or numbers ending in digits 0 and 5.  By using inverted calipers, this bias can be reduced.

Figure D.  After the size of the induration has been determined, the calipers are inverted and the result can be read and recorded.

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